(a) Field of the Invention
The present invention relates to a fuel injection system of a vehicle. More particularly, the present invention relates to a fuel injection system for preventing fuel leakage into the combustion chamber while an engine stops.
(b) Description of the Related Art
Typically, an engine of a vehicle operates by repeating processes of intake, compression, explosion, and exhaust, such that a reciprocal motion of a piston rotates a crankshaft. Such engines may be considered in different categories, for example, a gasoline engine, a diesel engine, etc., depending on a type of fuel.
A newer type of vehicle, an LPG engine vehicle, using liquefied petroleum gas as a fuel, is now being used. The LPG engine vehicle typically has a vaporizer vaporizing LPG compressed to 5 bar in the bombe (LPG tank), an apparatus for supplying LPG mixed with air in a mixer to a combustion chamber of an engine, an apparatus (LPI engine) for supplying LPG pressured under 15 bar (which is a combined pressure of an inside pressure of the bombe and a pressure made by a pump) through an injector to a combustion chamber. The injector used in an LPI engine is under pressure of 5˜15 bar when the engine stops.
The injector is an apparatus for injecting fuel into an inside of an engine. The injector has a function of controlling an amount of liquid fuel according to an operation of an accelerator, and a function of shutting off fuel supply when an engine stops. However, as the injector is used, the shutting off function deteriorates since the injector is repeatedly used (to control the amount of fuel) under conditions of high temperature and heavy vibration. The shutoff components can be gradually worn away,
In an LPG engine, since the fuel under predetermined pressure can leak out through the injector when an engine stops, a greater amount of fuel gas compared to air can be supplied to the combustion chamber. In such a case, the engine cannot be started, and if started, noxious gas is created and exhausted. In addition, since LPG is vaporized in the fuel injection system before being injected to the combustion chamber, a performance of the engine is deteriorated.
To resolve the above-mentioned problems, to prevent LPG leakage at the injector, and to prevent vaporization, many kinds of apparatuses and methods have been employed. However, previous attempts have not to date provided a basic solution.
The above mentioned problems can occur not only in an LPG engine but also in a gasoline vehicle, even though the viscosity and the evaporation point of LPG and gasoline are different from each other.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.